1. Field of the Invention
This invention relates to amphoteric N-type betaines of 2-hydroxy-1,1,2,3,3-pentahydroperfluoroalkylamines and their use as surfactants.
2. Description of the Prior Art
Katsushima et al., in U.S. Pat. No. 4,165,338, disclose hydroxy compounds having the formula: ##STR2## wherein Q is hydrogen; --CH.sub.2 CH(OH)CH.sub.2 Rf or a hydrocarbon residue which may contain one or more of ##STR3## R is hydrogen, a hydrocarbon residue or --CH.sub.2 CH(OH)CH.sub.2 R.sub.f ; m is 1 or 2; R.sub.f is hydroperfluoroalkyl, or .omega.-chloro-perfluoroalkyl having 4 to 20 carbons. Among the compounds disclosed by Katsushima et al., are ones having the formula: ##STR4## wherein R.sub.1 and R.sub.2 are each hydrogen or hydrocarbon group, including CF.sub.3 (CF.sub.2).sub.6 CH.sub.2 CH(OH)CH.sub.2 N(C.sub.2 H.sub.5).sub.2 and CF.sub.3 (CF.sub.2).sub.6 CH.sub.2 CH(OH)CH.sub.2 N(CH.sub.3).sub.2, among others. Katsushima et al. disclose acid addition salts of their compounds, but no betaine is disclosed.
Cords, in U.K. Patent Specification No. 1,434,119 discloses fluorinated sulfides having the formula EQU F(CF.sub.2).sub.n CH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 N.sup.+ R.sub.1 R.sub.2 R.sub.3
wherein each of R.sub.1 and R.sub.2 is C.sub.1 -C.sub.4 alkyl; R.sub.3 is C.sub.1 -C.sub.4 alkyl or is the covalently bonded counterion --(CH.sub.2).sub.q SO.sup.-.sub.3 or --(CH.sub.2).sub.m COO.sup.- ; m is 1 to 3; n is 4 to 14; and q is 2 to 4.
This invention overcomes a number of disadvantages associated with the compounds of Katsushima et al. and Cords. In the first place, the compounds of Katsushima et al. are not surface active unless reacted with an acid. Moreover, the compounds of Katsushima et al. are never amphoteric, and consequently, they may be used, if at all as surfactants, only under narrowly limited conditions of pH; i.e. less than a pH of about 5. The quaternary ammonium compounds of Cords would be similarly limited. While Cords' betaines would not be limited in that fashion, the process for preparing them (as well as his quaternaries) is a complicated, multi-intermediate procedure which involves certain hazards. Thus, the 2-chloroethyl dialkylamine hydrochloride used to prepare the perfluoroalkyl thioalkyl intermediate is a nitrogen mustard, i.e., an active vesicant. A corrosive system (a thionyl chloride reaction) is involved in preparing the nitrogen mustard intermediate. The 2-perfluoroalkyl ethanethiol is prepared by reacting the corresponding iodide with thiourea, an experimental carcinogen.